Backrest height adjusting apparatus for chairs and the like



Patented Jan. 3, 1967 3 295,888 BACKREST HEIGHT ADJUSTING APPARATUS FOR CHAIRS AND THE LEKE Larry L. Poland, Middleville, Mich, assignor to Steelcase, Ind, Grand Rapids, Mich, a corporation of Michigan Filed Oct. 21, 1965, Ser. No. 499,728 9 Claims. (Cl. 297298) This invention relates generally to chairs, especially those of the type known as secretarial posture chairs, and more' particularly to a new concept in mechanisms for adjusting the height of the backrest on such chairs.

Posture chairs, or secretarial posture chairs, generally include a backrest which is secured to the seat and leg portion by means of a vertically oriented and generally resilient upright post. Normally, the backrest portion of such chairs does not extend the full distance from the seat to shoulder height, but instead is considerably smaller and is positioned so as to support the small of the back of the person sitting in the chair, generally in a very erect position. Hence, these chairs have come to be known as posture chairs. In early models of these chairs, the backrest was fixedly secured to its upright support, but this clearly was an unsatisfactory design since many different persons use such a chair over its life span, and the position of the backrest should be vertically adjustable so as to accommodate the different heights of such persons. Consequently, later versions of posture chairs had adjustable backrests. All too frequently, however, the mechanism by which adjustment was provided was clearly visible from the rear of the chair and was rarther crude in nature, typically lbein-g an exterior hand wheel which controlled a set screw or the like. Consequently, such chairs had an extremely utilitarian and unfinished appearance which was completely incongruous and unsightly when compared to the modernistic design of other ofiicetype furniture so much in vogue in recent years.

Consequently, it is a major objective of the present invention to provide an adjustable backrest construction for chairs and the like which is substantially completely concealed from the exterior, so as to provide for modern streamlined design approaches and not detract from the aesthetic qualities of the chair.

Further important objectives of the invention are to provide a backrest adjusting mechanism which is extremely simple and easy to operate, and yet which has a positive locking action which prevents the possibility of any undesired slipping of the backrest from the height which has been selected. The adjusting mechanism also is very rugged and almost entirely free from any adverse effects caused by the normal wear and strain of long usage.

The foregoing major objects of the invention and the advantages provided thereby, together with other objects similarly desirable and advantages thereof, will become increasingly apparent following a consideration of the ensuing specification and its appended claims, particularly when taken in conjunction with the accompanying drawings illustrating a preferred embodiment thereof.

In the drawings:

FIG. 1 is a fragmentary sectional elevation of the height adjustment apparatus of the invention, as taken through the plane I-I of FIG. 2;

FIG. 2 is a fragmentary bottom end sectional view, taken through the plane II-H of FIG. 1;

FIG. 3 is a fragmentary sectional side elevation, taken through the plane III-III of FIG. 2;

FIG. 4 is a fragmentary lateral perspective view of a portion of the adjustment apparatus, showing details thereof; and

FIG. 5 is a reduced front elevation of a typical posture chair of the type utilizing the backrest height adjustment apparatus of the invention.

Briefly stated, the height adjustment apparatus of the invention includes an upright support post structure which is securable to the legs and seat portion of a chair assembly, a backrest member which telescopes over or is otherwise engageable with the post structure in a manner to be vertically movable relative thereto, a plurality of recesses in a generally aligned vertical sequence formed in the surface of the said post structure, a dog element loosely carried by the said backrest member at a predetermined and generally constant vertical position relative thereto, and a releasable positioning member for acting against said dog element to move the same into engagement with a given one of said recesses when the dog and such recess are aligned through vertical movement of the backrest member relative to the post structure. The dog element and ositioning member are arranged such that when the latter is released the dog element moves out of engagement wit-h the aligned recess, so that the height of the backrest may be varied by manually moving it vertically to a new position, wherein the dog element comes .into alignment with another recess in the sequence thereof. The positioning member is arranged such that when not intentionally released, it is continuously biased to maintain the dog element in engagement With the particular recess in lateral alignment therewith, and the dog element itself is preferably of such a size and weight distribution relative to the recesses that when the positioning member is intentionally released, the dog element is biased downwardly as by gravity out of engagement with the recess previously engaged thereby.

Referring now in more detail to the drawings, FIG. 5 illustrates a typical posture chair 1 having legs 5, a seat portion 6, and a backrest 10 mounted upon an upstanding support 14. The backrest member 18 with which the present invention is primarily concerned (FIGS. 1 and 2) supports the back of a person sitting in such a chair. While susceptible of being embodied in many difierent specific forms, the backrest member is typically a generally fiat and basically rectangular panel, which may be contoured to better conform to the curvature of the human back. The backrest ltl has a vertically disposed channel or passage 12 (FIG. 2) formed therein, into which the upright support post structure 14 is slidably receivable, such that the backrest 10 may be vertically moved relative to the support post. More specifically, the vertical channel or passage 12 may readily be provided by forming the backrest 10 in two lateral halves 16a and lttb, which are spaced apart a predetermined distance and joined by inner and outer sheet metal bridging elements 16 and 18, respectively (FIG. 2) which span the passage between the two halves 10a and 10b and are secured along each inner side thereof. Along their central portion, the two bridging elements 16 and 18 are channel-shaped, to extend into the passage 12 and define therein a flat vertical opening of a size which readily accommodates the support post structure 14. It is to be understood that while the backrest It} is illustrated as being a simple solid panel in form, it is most often covered by a decorative and concealing fabric, and is illustrated in the manner shown in the figures to better show the structural details beneath such fabric.

The support post structure 14 is usually a resilient metal member of the bar-like cross section seen in the figures, and in accordance with the present invention the upright support post has a vertically-aligned series of spaced recesses 20 formed in the surface thereof and along one of its lateral side edges (FIG. 1). Also, the upright support has a centrally located tapped hole formed therein, into which a bolt 22 is threaded through a vertical slot 24 formed in the outer bridging element 18, as shown. As will be apparent, the bolt 22 allows the backrest to be moved vertically relative to the upright support post while serving as a stop which limits the allowable relative vertical movement.

It will be observed that the spacing or channel 12 in the center of the backrest means is actually wider than necessary merely to accommodate the upright support post 14. This extra width provides room for a relatively narrow vertical channel 26 (FIG. 1) positioned adjacent and parallel to the upright support post 14. As FIG. 2 best illustrates, the narrow channel 26 is defined between a generally Z-shaped flange member 28 and the inner bridging element 16. Flange member 28 is secured between the inner bridging element 16 and the lateral portion 10a of the backrest means 10, and extends vertically, parallel to but spaced from the side or leg portion 16a of the channel-shaped bridging element 16.

Within the narrow channel 26 is located an elongate positioning member 30 and a dog element 32, most preferably in the form of a spherical ball. The positioning member 30 is formed of flat sheet or strap material such as metal, and has a width that is slightly less than the inner width of the narrow channel 26 (see FIG. 2). The upper end of the member 30 is bent to angle toward the side wall portion 16a of bridging element 16 (FIG. 1) and is then bent backward at an angle toward flange 28, thereby providing a ramp-like configuration designated 34. It will be noted from FIG. 3 that a tab portion 36 is struck from bridging element 16 and bent normal thereto, at the point where the positioning member 30 is first bent to form the ramp portion 34 thereof (see FIGS. 1 and 3). This serves to define a cavity between the ramp 34, the tab 36 and the side wall portion 16a of the bridging element, and this cavity cagingly retains the dog element 32 therein. The presence of the offset or horizontallyextending flange 36 also serves to retain the positioning member 30 within the narrow channel 26, since it is impossible for the positioning member to drop lower than the position in which it is shown in FIG. 1. This is the normal or active position for member 30, and it is positively maintained in this position due to the force of a compression spring 38 located between the tab 36 and the upwardly-directed bottom portion of the positioning member 30 (FIG. 1). Specifically, the lower portion of the positioning member 30 is curved upward in a smooth bend, whose extremity is split (FIG. 4) to provide an upstanding post 40 and a pair of laterally-directed tabs 42 and 44, with the arrangement being such that the post 40' telescopes into the bottom of the spring 38, which then acts downwardly against the lateral tabs 42 and 44.

Having now described in detail the structure and the general assembly of the present backrest height adjustment apparatus, its operation is as follows. The constant down ward bias exerted against the positioning member 30 by the spring 38 causes the ramp portion 34 of the positioning member to constantly push the dog or ball element 32 downward and horizontally, against the side portion 16a of the bridging element 16. Under these conditions, the dog is forced into an aperture formed in the side portion 16a which is aligned with the sequence of recesses formed in the upright support 14 (see FIG. 1).

The shape of each of the recesses 20 is of the same spherical configuration as that of the dog or ball element 32, but the aperture in side 16a and each of the recesses 20 have a diameter that is less than that of the ball 32, and consequently while the ball may be forced into the said aperture and into any of the recesses 20 aligned therewith, only a minor portion of the ball actually engages the aperture and recess, while the major portion of the ball remains within the narrow channel 26. This engagement of the ball 32 within any of. the recesses 20 is suflicient, however, to prevent any downward movement of the backrest means 10 relative to the upright support post 14, since the ball is in effect rather tightly wedged in place between the backrest means 10 (by the side 16a of its bridging elem-ent 16) and the upright support post 14 (by the recesses 20 formed therein). Moreover, the ball 32 cannot move out of this engaged position due to the presence of the ramp portion 34 of the positioning member 30, biased into this position by the spring 38.

When it is desired to adjust the height of the backrest member, all that is required is to manually move the positioning member 30 upward against the bias of spring 38, as by pressing the fingers against the curved protruding lower portion of the member. This raises the wed-gling ramp portion 34 of the positioning member upward within the narrow channel 26, and as soon as the ramp moves away from the dog element or :ball 32, the latter falls by gravity out of its engagement with the aperture in wall portion 16a and the particular recess 20 aligned therewith and drops onto the top of. the horizontal tab 36, since as will be remembered, the major portion or. the dog or ball element does not enter into engagement with either aperture or the recess, but instead remains within the channel. Thus, as soon as the positioning member 30 is raised, the backrest member 10 is free relative to the upstanding support post 14, and may be slid vertically relative thereto to a new position at the desired height.

As the backrest means is raised, the dog or ball element 32 remains caged between the vertical portion of the positioning member 30 and the tab 32. Consequently, the dog element is raised simultaneously with the backrest member to the new position. When the backrest member is at the desired height, the positioning member 30-is merely released fir om its upward position, and the spring 38 then returns it to its normal or active position, in which its inclined ramp portion 34 moves the :ball element 32 back into engagement with the aperture in the side wall 16a and with the nearest recess 20 in the support post 14, thereby once again locking the backrest 10 relative to the support post. It will be apparent that the precise new vertical position selected may not actually bring the ball element into eX-act alignment with one of the recesses 20, but the recesses may be spaced closely enough so that only .a slight vertical movement of the backrest away from the precise selected position will be enough to engage the ball with the recess that is closest to the selected position, with the change being so slight as hardly to be noticeable.

After having examined the foregoing specification, it is quite possible that those skilled in the art may conceive of other embodiments of the concept underlying the pres ent invention, or of certain modifications and changes in the specific embodiment set forth herein which nonetheless do not depart from the spirit of the invention and which utilize its concepts. Consequently, all such embodiments, variations, and changes are to be considered as within the scope of the claims appended herebelow, unless these claims by their language specifically state otherwise.

-I claim:

1. A backrest height adjustment apparatus tor chairs and the like, comprising in combination: an upright post structure securable to a chair assembly; a back-rest member engageable with said post stnucture to be vertically movable relative thereto; a plurality of recesses in a generally aligned vertical sequence formed in the surface of said post structure; a dog element loosely carried by said backrest member at a predetermined and generally constant vertical position relative thereto; said dog element being of a shape at least partially insertable within each of said recesses when aligned therewith through vertical movement of said backrest member relative to said post structure; and a releasable positioning member operatively associated with said backrest member for maintaining said dog in inserted engagement with an aligned recess and thereby maintaining a desired height adjustment of said backrest member relative to said post means; said positioning member when released allowing said dog to be moved out of engagement with the aligned recess to vary the height of the backrest member by manually moving same vertically to a new position of dog element and recess alignment.

2. The backrest adjustment apparatus of claim 1, wherein said dog element is of such a size and weight distribution as to shift downwardly from a recess in engagement therewith when said positioning member is released.

3. A backrest height adjustment apparatus for chairs and the like, comprising in combination: an upright post structure securable to a chain assembly; a backrest member having a channeled portion for vertical sliding engag ment with said post structure; a plurality of recesses in a generally aligned vertical sequence vformed in the surface of said post structure; said backrest member having a cavity communicating with its said channeled portion; a dog element loosely caged in said cavity; said dog element being of a shape at least partially insertable within each of said recesses when aligned therewith through vertical movement of said backrest member relative to said post structure; and a releasable positioning member operatively associated with said backrest member and positioned at least in part to move within said cavity; said positioning member acting against said dog element to maintain same in inserted engagement with an aligned recess and thereby maintain a desired height adjustment of said backrest member relative to said post means; said positioning member when released allowing said dog to be moved out of engagement with the aligned recess to vary the height of the backrest member by manually moving same vertically to a new position of dog element and recess alignment.

4. The backrest adjustment apparatus of claim 3, wherein said dog element is oi such a size and weight distribution as to fall by gravity from a recess in engagement therewith when said positioning member is released.

5. The backrest adjustment apparatus of claim 3, where said channeled backrest portion, said dog element, said recesses, and a substantial portion of said positioning member are all concealed from external view.

6. A backrest height adjustment apparatus for chairs and the like, comprising in combination: an upright post structure se-ou-rable to a chair assembly; a backrest member having a generally centrally disposed vertical passage therein for sliding engagement with said post structure; a plurality of recesses in a generally aligned vertical sequence formed in the surface of said post structure; a cavity rormed in said backrest member laterally of said vertical passage and communicating therewith through an aperture; said aperture being in lateral alignment with said sequence of recesses; a dog element loosely caged in said cavity; .said dog element having a minor portion of a size and shape to pass through said aperture and into one of said recesses in alignment therewith; said dog element having a major portion of a size and shape preventing it from passing through said aperture; and a releasable positioning member movably mounted upon said backrest member and positioned at least in part to move within said cavity; said positioning member acting against said dog element to maintain the said minor portion thereof in inserted engagement with an aligned recess and thereby maintain a desired height adjustment of said backrest member relative to said post means; said positioning member when released allowing said minor portion to be moved out of engagement with the aligned recess to vary the height of the backrest member by manually moving same vertically to a new position of dog element and recess alignment.

7. The backrest adjustment apparatus of claim 6, wherein said releasable positioning member is resiliently biased to continuously act against said do-g element and is released by manually overcoming said bias.

8. The backrest adjustment apparatus of claim 7, wherein said dog element is of such a size and weight distri-bution as to fall by gravity from a recess in engagement therewith when said positioning member is released.

9. The backrest adjustment apparatus of claim 8, wherein said dog element is a spherical ball rollably caged in said cavity, said aperture is generally circular and of an effective diameter smaller than that of said ball to establish said major and minor portions, and wherein said recesses are each spherical concavities with a diametral opening substantially the same as the diameter of said aperture.

References Cited by the Examiner UNITED STATES PATENTS 2,364,261 12/1944 Wood 297298 2,599,601 6/ 1952 Van Vuren 297--306 2,662,586 12/ -3 Cramer 297-304 X 2,692,012 10/1954 Cramer 297-298 2,988,398 6/'1961 Hamilton 297--305 X 3,224,807 12/1965 Welch et a1. 297-304 FRANK B. SHERRY, Primary Examiner.

G. O. FINCH, Assistant Examiner. 

1. A BACKREST HEIGHT ADJUSTMENT APPARATUS FOR CHAIRS AND THE LIKE, COMPRISING IN COMBINATION: AN UPRIGHT POST STRUCTURE SECURABLE TO A CHAIR ASSEMBLY; A BACKREST MEMBER ENGAGEABLE WITH SAID POST STRUCTURE TO BE VERTICALLY MOVABLE RELATIVE THERETO; A PLURALITY OF RECESSES IN A GENERALLY ALIGNED VERTICAL SEQUENCE FORMED IN THE SURFACE OF SAID POST STRUCTURE; A DOG ELEMENT LOOSELY CARRIED BY SAID BACKREST MEMBER AT A PREDETERMINED AND GENERALLY CONSTANT VERTICAL POSITION RELATIVE THERETO; SAID DOG ELEMENT BEING OF A SHAPE AT LEAST PARTIALLY INSERTABLE WITHIN EACH OF SAID RECESSES WHEN ALIGNED THEREWITH THROUGH VERTICAL MOVEMENT OF SAID BACKREST MEMBER RELATIVE TO SAID POST STRUCTURE; AND A RELEASABLE POSITIONING MEMBER OPERATIVELY ASSOCIATED WITH SAID BACKREST MEMBER FOR MAINTAINING SAID DOG IN INSERTED ENGAGEMENT WITH AN ALIGNED RECESS AND THEREBY MAINTAINING A DESIRED HEIGHT ADJUSTMENT OF SAID BACKREST MEMBER RELATIVE TO SAID POST MEANS; SAID POSITIONING MEMBER WHEN RELEASED ALLOWING SAID DOG TO BE MOVED OUT OF ENGAGEMENT WITH THE ALIGNED RECESS TO VARY THE HEIGHT OF THE BACKREST MEMBER BY MANUALLY MOVING SAME VERTICALLY TO A NEW POSITION OF DOG ELEMENT AND RECESS ALIGNMENT. 